On Fri, Apr 4, 2025 at 4:58 AM Willy-Bas Loos <willy...@gmail.com> wrote:
> Hi! > > I'm looking for a way to find out if there are still replication slots > active for a publication before dropping the publication in an automated > way. The idea is that the publication is thought not to be needed any > longer, but we want to make sure. > > I'm having trouble finding a link between a publication, the subscriptions > and the replication slots. Especially when you don't want to make > assumptions about any subscriber nodes, so you are restricted to the > publisher node. > > The best I could find was a query listed in pg_stat_activity that lists > the slot name and the publication name: > START_REPLICATION SLOT "my_slot" LOGICAL 5DD1/3E56D360 (proto_version '1', > publication_names '"my_publication"') > > I don't like the idea of using string manipulation on such query strings > to get the information I need. Postgres must have a way to compose this > query. > Can anyone tell me a way to find replication slots that belong to a > publication? > > -- > Willy-Bas Loos > Hi Willy-Bas, Logical replication slots appear in the views pg_stat_replication and pg_replication_slots. Both views have the information you are looking for, the difference is pg_stat_replication shows only the active slots. Keep in mind Temporary Slots only live for the length of the session that created it; the slot will appear in both views. The bigger issue I think you are trying to address is when can a slot be dropped safely. Once a logical replication slot is dropped there is no recovery of the slot's lsn position. Probably the best way to decide if a slot has been abandoned is how far behind it is. The pg_wal_lsn_diff can be used to figure out how far behind a slot is https://www.postgresql.org/docs/13/view-pg-replication-slots.html https://www.postgresql.org/docs/13/monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-VIEW https://www.postgresql.org/docs/current/functions-admin.html#FUNCTIONS-ADMIN-BACKUP Hope this answers your question Justin
